User’s Manual v.15
QVidium
®
H.264 HD Video Codecs
™
Copyright 2011-2014 QVidium
®
Technologies, Inc.
Page 58 of 71
13
Appendices
13.1 Appendix A: Encoder Configuration Parameters
This section explains the parameters related to the analog input signals and encoding settings and
how they relate to the operation of the encoder and error correction and network transport setup.
Video Encoding Bit Rate:
Total peak stream bit rate for Variable Bit Rate (VBR) video encoding.
The resulting transport stream bit rate is the sum of the bit rates of the video program, audio
program and program stream information. The video bit rate is specified in bits per second and can
range from 128 Kbps for CIF resolution to 19 Mbps for 720x480 (NTSC) or 720x576 (PAL)
standard definition resolutions, or can range from 4 Mbps to 19 Mbps for high definition video
resolutions. The higher the bit rate, the better the video quality.
Audio Bit Rate (compressed):
The audio bit rate determines encoding audio quality and allows
you to trade off audio throughput for quality. The audio bit rate can be set to one of 64,000,
128,000, 192,000, 256,000 or 384,000 bits per second. Increasing the audio bitrate, up to a
maximum value of 384 Kbps increases the audio fidelity. Regardless of the audio signal level on
either channel, selecting an audio bitrate of 64 Kbps or higher will always force the encoder to
send 2 channels of audio (stereo audio). Each audio channel uses one-half of the selected audio
bitrate. The H.264 HD Video
Codec™ encodes audio using either MPEG-1 Layer II encoding,
MPEG2 AAC, or MPEG4 AAC audio encoding.
For minimizing the audio bitrate, we provide the option of setting the number of audio channels to 1
and the audio bitrate to 16 Kbps or 32 Kbps. Do not use an audio bitrate less than 64 Kbps unless
you set the number of audio channels to 1. Even then, setting the number of audio channels to 1
has the potential to cause unexpected halting of the encoder. So, please be aware that this option
may impact the reliability of the encoder.
Audio Sampling Rate (Hz):
The audio sampling rate specifies the clock rate for capturing and
digitizing the incoming analog audio signal. Because of anti-aliasing filtering, the maximum audio
frequency that can be digitized is limited to a frequency of about 1/3 to 1/2 of the audio sampling
rate. Internal anti-aliasing filters severely attenuate audio signals above a frequency of about 1/3 of
the sampling rate. Thus, for a standard music CD rate of 44.1 KHz, the maximum audio frequency
that the encoder can pass is about 14.7 KHz. The valid selectable audio sampling clock rates are
32 KHz, 44.1 KHz, and 48 KHz.
SDI formatting requires that the audio sampling rate be fixed at 48 KHz, so the current user
interface disables setting this value.
(SD Only) Video Frame Rate (Full Frame Rate and fractions thereof):
Select Full Frame Rate
for normal video. This will encode the video signal at 29.97 frames per second for NTSC and 25
fps for PAL video format. If you need to produce lower video bitrates, and reducing the resolution is
not sufficient or undesired, you can use this feature to sacrifice frame rate for lower bitrates.
Video Encoding:
The H.264 HD Video
Codec™ converts a digital SDI or HDMI video input signal
according to the ITU-R.BT-656 standard, performs a 4:2:2 to 4:2:0 conversion and compresses the
digitized video using either the MPEG-2 video encoding standard (MP@ML, ISO/IEC-13818-2) or
MPEG4-AVC (H.264) high profile compression, depending upon your selection.
We suggest that you select H.264 compression. The QVPRO codec incorporates High Profile,
Level 4.0 to 4.1 MPEG4-AVC (part 10) video encoding. This nearly always produces better video
